Three-dimensional ski surface

ABSTRACT

A ski for use in cross-country or tour skiing. The running surface of the ski is characterized by a three-dimensional surface of protuberances. The protuberances are aligned in rows substantially transverse to the longitudinal axis of the ski. The protuberances of one row are offset from the protuberances of the preceding and succeeding rows to create a scale-like pattern. The protuberances are also nonharmonically spaced to eliminate pure tone-type noise attendant with regularly repeated patterns. Further, each of the protuberances has an arcuate-shaped gliding surface defined by a perimeter of straight edges. The arcuate surface maximizes the forward glide of the ski while the straight edges enhance the tracking and climbing ability of the ski.

United States Patent 11 1 Ver et al.

[ THREE-DIMENSIONAL SKI SURFACE [75] Inventors: Istvan L. Ver, Arlington; William 1).

Banner, Byfield, both of Mass.; Hans Woitschatzke, Wiesbaden-Kohlheck, Germany [73] Assignees: Skisearch, Inc., Boston, Mass. by

said Danner and Woitschatzke; Bolt Beranek and Newman, Inc., Cambridge, Mass. by said Ver France 280/1 1.13 Y Austria 280/1 1.13 Y

Primary Examiner-David Schonberg Assistant Examiner-Milton L. Smith [57] ABSTRACT A ski for use in cross-country or tour skiing. The running surface of the ski is characterized by a threedimensional surface of protuberances. The protuberances are aligned in rows substantially transverse to the longitudinal axis of the ski. The protuberances of one row are offset from the protuberances of the preceding and succeeding rows to create a scale-like pattern. The protuberances are also nonharmonically spaced to eliminate pure tone-type noise attendant with regularly repeated patterns. Further, each of the protuberances has an arcuate-sl'iaped gliding surface defined by a perimeter of straight edges. The arcuate surface maximizes the forward glide of the ski while the straight edges enhance the tracking and climbing ability of the ski.

9 Claims, 5 Drawing Figures PATENTEDJAN mrs' INVENTORS ISTVAN L. V WILLI NER HANS ER AM D. DAN

WOITSCHATZKE BY CROWLEY AND STEVENS A TTORNEYS BACKGROUND OF THE INVENTION I In skiing one aspect to which considerable importance has been attached is cross-country or tour skiing. In tour skiing the running surface which engages the snow is either carefully waxed or structurally modified from the type of running surface employed in alpine skiing to provide greater control and stability with respect to climbing and tracking. Primary attempts to modify ski running surfaces are disclosed in U.S. Pat. No. 3,381,972 and German Patent No. 870,369. An improvement of these patents was the utilization of a three-dimensional scale formation on the running surface of the ski as exemplified in U.S. Pat. No. 3,408,086. This patent incorporates rows of protuberances having convexly curved edges, each row offset from one another along the running surface. Although this produces enhanced tracking and climbing ability, the gliding friction is increased. Further, the regularly repeated pattern over the entire gliding surface generates a sound with strong pure tone components. The pitch of the tone as well as its intensity increases with increasing gliding speed. Typically, the pitch of the fundamental tone and its harmonic fall within the frequency range wherein the human ear is most sensitive.

SUMMARY OF THE INVENTION One aspect of the present invention is directed to a three-dimensional ski base on the running surface of the ski embodying uniquely designed protuberances having a substantially rectangular shape in a nonuniform pattern. The tracking and climbing ability of the ski is controlled through the selection of the edges of the protuberances which may be modified to control the friction coefficient for sideward tracking and backward climbing motion. Another aspect of the invention is devoted to the degree of inclination and shape of the contacting surfaces of the protuberance to provide lower friction for forward gliding with maximum climbing ability. A further aspect of the invention is that the protuberances are nonharmonically spaced along the runnning surface to eliminate pure tone noise and create only a random or less disturbing random noise.

Briefly, the invention in its preferred embodiment comprises rows of rectangular shaped protuberances having curved contacting surfaces thereon, nonharmonically arranged on the running surface.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 1B are schematic illustrations of various projections employed in the invention;

FIG. 2 is an enlarged schematic illustration of FIG. 1A;

FIG. 3 is a side sectional view of FIG. 1A; and

FIG. 4 is a schematic illustration of rows of projections illustrating the nonharmonic spacing concept.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S) Referring to FIG. 1A, a section of the running surface of a ski .10 is shown wherein protuberances 14 are formed in rows transverse to the longitudinal axis of the ski 10. As shown, the protuberances of each row are offset from the protuberances of the preceding or succeeding row to provide a staggered arrangement of protuberances. In this embodiment "the totality of the pattern effected by the protuberances is substantially that as shown in U.S. Pat. No. 3,408,086. The tracking and climbing ability of a ski is directly proportional to the total length of the edges. It is known from all geometries that the circle has the smallest perimeter, that is edge, to area ratio. The configuration shown in FIG. IA has a larger perimeter-to-area ratio for the same scales than a circular geometry of the scale pattern of a similar base. The protuberances of this invention yield better tracking and climbing ability as compared to one of a circular configuration, because of the increased perimeter, or edges. Additionally, the ratio of the friction coefficient for the sideward (tracking) and backward (climbing) motion for the pattern of FIGS. IA and 18, particularly FIG. 1A, can be chosen freely by the proper choice of the edge lengths x and y as shown in FIG. 2. For example, a large x to y ratio would favor climbing versus tracking, and a large y to x ratio would favor tracking versus climbing. Thus the embodiments of FIGs. 1A and 18 provide a large perimeter-to-area ratio which significantly enhances the tracking and climbing ability of skis having this particular configuration on the base thereof. Accordingly, there may be a combination of straight and nonstraight edges e.g. FIG. 1B, or a plurality of small straight edges to define the perimeter. Further, the straight edges have been shown to define the perimeter. Further, the straight edges have been shown as offset or at an angle to the longitudinal axis of the ski. The edges may be at any angle and in some instances may be parallel, for example, where a protuberance is flush with the edge of the ski as shown in FIG. 1A.

Another feature of the invention is shown in FIG. 3 wherein the curved surface area of the protuberances 14 is illustrated in longitudinal cross-section. This curved surface contacting area yields lower friction for forward gliding without minimizing or inhibiting the effectiveness of the straight edges shown in FIGS. 1A and 1B. In contrast to prior art devices, the thickness of the protuberance of this invention increases gradually, preferably following an exponential curve rather than leveling off in a straight line. The gradual curvature of the protuberances 14 of FIG. 3, for example similar to the shape of the gliding surface of a sled, avoids the creation of edges on the surface contacting area which edges would increase the friction for forward glide without having any beneficial effect on the tracking and climbing characteristics. In this embodiment the thickness t of the protuberances as a function of the distance from the forward point x can for example take the form of an exponential function,

where t is the thickness of the protuberance at the trailing edge and a is a number preferably larger than the length of the protuberance I With the proper choice of a one may obtain a gradually decreasing curvature in the forward part and a nearly flat gliding surface near to the trailing or rear edge, resulting in improved gliding performance for forward motion. Of course, any curvature may be employed, this feature of the invention being directed to eliminating the occurrence of any straight edges on the surface contacting area which would inhibit the forward gliding motion and add nothing to the climbing and tracking characteristics of the ski.

The prior art references show a uniform distribution of some type of projections or scale formation on the running surface of the ski, particularly U.S. Pat. No. 3,408,086, where the pattern of the scale base is regularly repeated over the entire gliding surface. This regularly repeated pattern generates noise when it passes over a surface such as snow or water. Whereas in the three-dimensional scale base the pattern is regularly repeated over substantially the entire gliding surface, the generated sound has strong pure-tone components. The pitch of the tone, as well as its intensity, increases with increasing gliding speed. For the skis presently employed today the pitch of the fundamental tone and its harmonics fall into the frequency range where the human ear is most sensitive.

To eliminate the sound from the disturbing pure tone and to arrive at arandom noise, the spacing between the various rows of projections, that is, the scale, should be unequal and nonharmonic to prevent periodicity within each group of rows, as illustrated in FIG. 4. The sequence of rows in the various groups should be different to prevent periodicity of groups. As an illustrative embodiment of this principle, FIG. 4 shows four rows of different spacings or scale lengths identified as a, b, c, and d. For illustrative purposes only, b has been shown as 1.13 times the length of a, c as 1.23 times the length of a, and d as 1.31 times the length of a. Of course, any random nonuniform arrangement of rows within the group of protuberances, whether in rows or not, to prevent periodicity may be employed; and less than four rows may be varied within a group, such as two or three or more than four, as desired.

In a particularly preferred embodiment the gliding surface of the ski would consist of groups built from a random combination of rows a, b, c, and d, such as abcd/badc/adcb/dabc/bacd/ etc. After four or five different group combinations the pattern is sufficiently randomized so that it may be repeated again and again until the entirerunning surface is covered.

As shown in FIGS. 1A and 4, the rows are in parallel relationship, each of the rows normal to the longitudinal axis of the ski. The rows when parallel to one another may assume other parallel configurations, such as at any angle to the axis of the ski, the rows following straight, to include cheveron-like configurations, or curved-like configurations. The curve-like parallel configurations may be sinusoidal, arcuate, parabolic, etc., or combinations thereof. As shown in FIGS. 1A and 4, the centers of the projection of one row are bisected by the joined edges of the next row. The center lines of the projections of a first row may be aligned with the center lines of the projections of one or more of the other row or rows of the ski. Alternatively, they may be offset from the projections of any of the other rows by any amount as desired, some projections aligned and some nonaligned.

In the invention the nonharmonic spacing of a scale formation may be employed with any type of protuberance to eliminate the characteristic pure tone-like noise attendant with the regularly repeated patterns. This concept may be used alone or in combination with the formation of projections having edges defining their perimeters as disclosed in FIGS. 1A and 18. Further, it may be used in combination with projections wherein the contacting surface of the projection eliminates any straight edges thereon to minimize the gliding friction without impairing the tracking and climbing ability of the ski. Thus, any of the embodiments such as represented by FIGS. 1A or 18 may be used alone or in combination with the features of the invention as represented by FIG. 4, alone or in combination with features of the invention as represented by FIG. 3. Further, the embodiment as represented by FIG. 3 may be used alone or in combination with the embodiments of FIG. 1 and/or those of FIG. 4. Although in the preferred embodiment to minimize the gliding friction, maximize the tracking and climbing ability, and to eliminate the pure tone components generated with a regular surface, combinations of FIGS. 1A, 3, and 4' are employed together.

Although described with particular reference to the embodiment of the invention on the running surface of a ski for cross-country or tour skiing, it is obvious that the invention may be employed to alpine skis, surfboards, and similar devices for sliding or gliding over water, snow, ice, etc. The invention may be employed on any surface having protuberances which are exposed to a fluid medium; for example, where there is relative motion between the medium and the surface and it is desired to control the flow sound and/or frictional characteristics between the medium and surface, such as in the paper industry on a pulp flow apron to improve the mixing of the pulp.

Having described the invention, what we now claim l. A ski having a three-dimensional patterned bottom surface, the pattern including a plurality of protuberances extending from the surface thereof, said protuberances irregularly repeated over the bottom surface in a nonharmonic pattern whereby pure-tone sonic components generated by sliding contact of the ski bottom surface with a supporting surface are eliminated or minimized.

2. The ski of claim 1 wherein the protuberances form a plurality of rows, each row extending substantially transverse to the longitudinal direction of the ski.

'3. The ski of claim 2 wherein the rows are spaced apart in a nonuniform and nonharmonic pattern to prevent periodicity.

4. The ski of claim I wherein the protuberances are substantially similar in size and shape.

5. The ski of claim 1 wherein the protuberances are aligned in rows transverse to the longitudinal direction of the ski, each succeeding row offset from the preceding row whereby a nonuniform scale-like pattern of protuberances is formed on the bottom surface of the ski.

6. A ski having a three-dimensional patterned bottom surface, the pattern including a plurality of protuberances extending from the surface thereof, said protuberances irregularly repeated over the bottom surface in a non-harmonic pattern whereby pure-tone sonic components generated by sliding contact of the ski bottom surface with a supporting surface are eliminated or minimized, the protuberances being aligned in rows extending substantially transverse to the longitudinal direction of the ski, the protuberances of a first row having a length n, the protuberances of a second row having a length of n times x, the protuberances of a third row having a length of n times y, and the protuberances of a fourth row having a length of n times 2, etc., wherein x, y, and z are dissimilar values selected to insure a non-harmonic spacing.

7. The ski of claim 6 wherein the number of rows of different length comprise a group, the bottom surface of the ski having a plurality of groups thereon, the rows within a first group in a different arrangement in relation to the rows of at least one of the other groups.

8. A ski comprising a main body portion, a front end, and a rear end, and a three-dimensional patterned bottom, the pattern including a plurality of protuberances being aligned in rows substantially transverse to the longitudinal axis of the ski, at least some of the protuberances of said rows being offset from the protuberances of the succeeding and preceding row; at least some of said protuberances characterized by straight edges on either side thereof, one of said edges at an angle to the longitudinal axis of the ski, the edges presenting a rearward edge substantially transverse to the longitudinal axis of the ski, said side edges and rearward edge comprising the perimeter of the protuberance, the protuberance including a contacting surface enclosed in said perimeter and said surface extending rearwardly and upwardly and terminating at the rearward edge, the rows of protuberances being nonharmonically spaced along the bottom of the ski whereby pure-tone sonic components generated by sliding contact of the ski bottom surface with a supporting surface are eliminated or minimized.

9. A ski having a main body portion, a front end, and a rear end, and a three-dimensional patterned bottom, the pattern including a plurality of protuberances, the protuberances extending rearwardly and upwardly from the bottom surface of the ski, at least some of said protuberances having surface contacting areas which describe an arcuate shape form a minimum angle in a forward direction of motion of the ski and terminating in a rear edge, said protuberances being aligned in rows transverse to the longitudinal axis of the ski, some of the protuberances of said rows offset from the protu berances of the succeeding or preceding row, the rows being nonharmonically spaced whereby pure-tone sonic components generated by sliding contact of the ski bottom surface with a supporting surface are elimi- 

1. A ski having a three-dimensional patterned bottom surface, the pattern including a plurality of protuberances extending from the surface thereof, said protuberances irregularly repeated over the bottom surface in a nonharmonic pattern whereby pure-tone sonic components generated by sliding contact of the ski bottom surface with a supporting surface are eliminated or minimized.
 2. The ski of claim 1 wherein the protuberances form a plurality of rows, each row extending substantially transverse to the longitudinal direction of the ski.
 3. The ski of claim 2 wherein the rows are spaced apart in a nonuniform and nonharmonic pattern to prevent periodicity.
 4. The ski of claim 1 wherein the protuberances are substantially similar in size and shape.
 5. The ski of claim 1 wherein the protuberances are aligned in rows transverse to the longitudinal direction of the ski, each succeeding row offset from the preceding row whereby a nonuniform scale-like pattern of protuberances is formed on the bottom surface of the ski.
 6. A ski having a three-dimensional patterned bottom surface, the pattern including a plurality of protuberances extending from the surface thereof, said protuberances irregularly repeated over the bottom surface in a non-harmonic pattern whereby pure-tone sonic components generated by sliding contact of the ski bottom surface with a supporting surface are eliminated or minimized, the protuberances being aligned in rows extending substantially transverse to the longitudinal direction of the ski, the protuberances of a first row having a length n, the protuberances of a second row having a length of n times x, the protuberances of a third row having a length of n times y, and the protuberances of a fourth row having a length of n times z, etc., wherein x, y, and z are dissimilar values selected to insure a non-harmonic spacing.
 7. The ski of claim 6 wherein the number of rows of different length comprise a group, the bottom surface of the ski having a plurality of groups thereon, the rows within a first group in a different arrangement in relation to the rows of at least one of the other groups.
 8. A ski comprising a main body portion, a front end, and a rear end, and a three-dimensional patterned bottom, the pattern including a plurality of protuberances being aligned in rows substantially transverse to the longitudinal axis of the ski, at least some of the protuberances of said rows being offset from the protuberances of the succeeding and preceding row; at least some of said protuberances characterized by straight edges on either side thereof, one of said edges at an angle to the longitudinal axis of the ski, the edgEs presenting a rearward edge substantially transverse to the longitudinal axis of the ski, said side edges and rearward edge comprising the perimeter of the protuberance, the protuberance including a contacting surface enclosed in said perimeter and said surface extending rearwardly and upwardly and terminating at the rearward edge, the rows of protuberances being nonharmonically spaced along the bottom of the ski whereby pure-tone sonic components generated by sliding contact of the ski bottom surface with a supporting surface are eliminated or minimized.
 9. A ski having a main body portion, a front end, and a rear end, and a three-dimensional patterned bottom, the pattern including a plurality of protuberances, the protuberances extending rearwardly and upwardly from the bottom surface of the ski, at least some of said protuberances having surface contacting areas which describe an arcuate shape form a minimum angle in a forward direction of motion of the ski and terminating in a rear edge, said protuberances being aligned in rows transverse to the longitudinal axis of the ski, some of the protuberances of said rows off-set from the protuberances of the succeeding or preceding row, the rows being nonharmonically spaced whereby pure-tone sonic components generated by sliding contact of the ski bottom surface with a supporting surface are eliminated or minimized. 